Answer: crossing over allows for genetic variation
Explanation:
crossing over is the exchange of genes between two chromosomes which ends up resulting in non-identical chromatids that comprise the genetic material of gametes (sperm and eggs).
Basically crossing over makes the chromatids that are held together by a centromere, no longer identical to eachother which creates genetic variation.
Phenotypically and genotypically there are only two different ratios. If you think of a Punett square...
<span>You could say that a pea plant with the trait for the dominant color green (G) could also carry the recessive trait for yellow (g). So let's say you mate a dominant green, (Gg) with another dominant green, (Gg). You would get 1 (GG), 2 (Gg) and 2 (gg). </span>
<span>Phenotypically (as in physical traitwise), the ratio is 3:1 because you have 3 green colored peas and one yellow. </span>
<span>Genotypically (as in traitwise), the ratio is 1:2:1, because you have 1 (GG), 2 (Gg) and 1 (gg). </span>
<span>So although it's random, for any specific trait there are only 4 different outcomes.</span>
It affect The survival and extinction of species
Necessary????????????????????????
Herbicides are a broad category of pesticides that are used to get rid of undesirable plants like weeds and grasses that hinder the development and productivity of desired agricultural crops. Both 2,4-D and 2,4,5T are also known as 2,4-Dichlorophenoxyacetic acid and
- Herbicides like 2,4-D and 2,4,5-T are also referred to as auxin-type herbicides or plant growth regulators. Auxins are hormones that affect cell division and elongation in order to control cell growth.
- Auxins are required by plant cells in the proper concentration for growth and development. If auxin levels are too low, plant growth is not promoted at all, and if levels are too high, plant growth is excessively stimulated.
- Most grasses are not killed by 2,4-D and 2,4,5 T, but broadleaf weeds are. It moves to the plant's meristems after being absorbed through the leaves.
- These herbicides affect the tissues' cells, causing them to continually divide and proliferate. The plant finally dies as a result of this unchecked, unsustainable growth, which also causes stem curling and withering of the leaves.
Thus, by promoting cell division, these compounds act as herbicides.
Learn more about herbicides:
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